This invention relates to an apparatus which may be used in the control of the quality of liquid metals, for example, liquid steel or copper, in commercial production. More particularly, this invention relates to an apparatus for displaying the active oxygen content of a liquid metal and the sensor temperature developed by an oxygen sensing probe immersed in the liquid metal. Still more particularly, this invention relates to a method and apparatus for displaying such data.
The advent of new and rapid processes for the refining of liquid steel, such as the basic oxygen furnace, has emphasized the need for extremely rapid methods of analyses of the metal while the metal is still liquid in the furnace or in the ladle. Earlier steel refining processes, such as the basic open hearth, required upward to ten hours or more to refine completely a heat of 200 or 300 tons from melt-down to tap, whereas the same amount of steel is now being processed in the basic oxygen furnace in as little as thirty minutes. As a result, an open hearth operator had as much as an hour in the latter part of the heat in which to obtain sufficient analytical data to make decisions regarding the types and quantities of the final additions to be made, to make the additions, and then to tap the heat within the desired specifications. Today, the refining reactions occur so rapidly in the basic oxygen furnace that the operator has only about five minutes in which to obtain his analytical data and in which to make the necessary additions prior to tapping. Sometimes this final stage of the heat is reduced to as little as one or two minutes.
Thus, the need for very rapid analytical methods in modern steel-making is apparent. Such data must be available instantaneously and provide the necessary information in a matter of seconds.
In most steels, the data needed for such control are the temperature, the amount of carbon and the active oxygen which are present. The immersion thermocouples which have been in use for some 20 or 30 years will indicate the temperature of liquid steel in about 10 seconds. In addition, rapid methods for the determination of the carbon content have been available for the past several years.
However, the determination of the active of the dissolved oxygen in liquid metals was not possible until the invention of the solid oxygen-ion electrolyte sensor or probe which is capable of being plunged directly into the liquid metal. Such a device is described in the literature of the following articles, for example:
1. G. R. Fitterer, "Progress in the Development of a Device for the Direct Determination of Oxygen in Liquid Steel", AIME, J. Metals, August 1966; and
2. G. R. Fitterer, "Measuring the Active Oxygen Content in Commercial Steel," Instrument Society of America, "Iron and Steel Instrumentation Symposium", March 1970, Pittsburgh, Pa.
This device is also disclosed in detail in U.S. Pat. to G. R. Fitterer, No. 3,619,381, issued Nov. 9, 1971.
Fortunately, this device also responds very rapidly so that the oxygen content of the liquid metal is indicated within fifteen to twenty seconds. With this information, the steel melter can decide about the amount and types of deoxidizing alloys to add so as to insure that the desired degree of soundness and other qualities are provided when the metal solidifies as an ingot, as a casting, or during the continuous casting process. Thus, the three most important items of information needed by the steel melter in all of the steelmaking processes are available to him within seconds for the first time in history.
Accordingly, it is an object of this invention to provide a method and appratus for displaying such data for the convenience of their users. It is generally desired that such an apparatus be portable so that it may be carried by the operator to different stations in the plant or situated permanently at one station as desired.
Because of the constraints on this invention and its environment, it is also desired that the apparatus be completely self-contained so that it may be operated on rechargeable batteries or on line current as desired.
In addition, it is desired that such an apparatus provide a completely automatic sequence of events so that only one operator is needed to make the oxygen determination.
Thus, it is a principal object of this invention to provide such a method and apparatus described above.